Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
In a general image processing apparatus such as a scanner, an image processing unit divides one sheet's worth of document image, which is read by an image reading unit, into band regions partitioned by a predetermined width each in a sub-scanning direction. Then, the image processing unit performs image processing such as a shading correction to each band region.
Further, the following method is described in this technique. In order to shorten process time of image compression, a white image determining unit determines whether or not an image in each band region is a uniform white image, and when the image is determined to be the white image, a preliminarily stored compressed white image is used.